Natamycin

What this is

Natamycin is a polyene macrolide antifungal: it binds ergosterol, a sterol in fungal cell membranes, so it inhibits molds and yeasts rather than bacteria. Food authorities generally permit it only in narrow uses with residue limits, especially cheese and selected cured-meat applications; the United States caps it at 20 ppm in finished cheese, while the European Union and Codex use surface-treatment limits for specified products. The main biological concern is exposure to an antifungal drug class through food and the possibility of selecting less-susceptible fungi or altering the gut fungal community. Current agency reviews do not show a strong signal at allowed food-use levels: JECFA in 2024 reaffirmed an ADI of 0–0.3 mg/kg body weight, found high-end dietary estimates below that value, concluded there was no concern for antimicrobial resistance, and judged gut-microbiome disruption risk low. EFSA’s older 2009 review also found no safety concern for surface use, but noted limitations in the older toxicity evidence. A peer-reviewed caution argued that higher-exposure, well-mixed uses such as beverages or yogurt could pose a greater resistance concern than surface treatment.

Safety Review

The critical endpoints experts review in safety assessments. This is not a prediction of harm.

Natamycin is poorly absorbed and mainly remains in the gut, so the practical question is whether repeated food exposure could disturb gut fungi or encourage fungi with reduced susceptibility to polyene antifungals. JECFA’s 2024 review concluded that dietary exposure estimates were below the ADI, that natamycin was not of genotoxic concern, that no antimicrobial-resistance concern was identified, and that gut-microbiome disruption risk was low. EFSA’s 2009 review reached a similar conclusion for surface treatment, while noting that the older data package had limitations and did not support deriving an EFSA ADI at that time. A peer-reviewed caution focused on higher-exposure, well-mixed uses such as beverages or yogurt; that concern is more relevant to expanded or off-label use than to tightly limited surface treatment of cheese or cured meats.

No safety review endpoints are listed for this ingredient yet.